mx_sheen_bsdf.osl

#include "lib/mx_microfacet_sheen.osl"

// TODO: Vanilla OSL doesn't have a proper sheen closure,
// so use 'diffuse' scaled by sheen directional albedo for now.
void mx_sheen_bsdf(float weight, color Ks, float roughness, vector N, output BSDF bsdf)
{
    if (weight < M_FLOAT_EPS)
    {
        bsdf.response = 0;
        bsdf.throughput = color(1.0);
        return;
    }

    // TODO: Normalization should not be needed. My suspicion is that
    // BSDF sampling of new outgoing direction in 'testrender' needs
    // to be fixed.
    vector V = normalize(-I);

    float NdotV = fabs(dot(N,V));
    float alpha = clamp(roughness, M_FLOAT_EPS, 1.0);
    float albedo = weight * mx_imageworks_sheen_dir_albedo(NdotV, alpha);
    bsdf.response = albedo * Ks * diffuse(N);
    bsdf.throughput = 1.0 - albedo;
}